The objectives of this research program are to continue and extend the ongoing investigations on the surface properties of hydroxyapatite, with special reference being given to the elucidation of the mechanism of interaction of fluoride and constituents of salivary proteins with hydroxyapatite have revealed some results which may have far reaching consequences. It is proposed to explore the adsorption of fluoride on HA from aqueous media more thoroughly through the systematic control of a number of solution variables. A study of fluoride adsorption on dental fillers is also contemplated. Direct evidence for distinguishing between chemisorbed fluoride and the formation of fluorapatite or fluorite at the hydroxyapatite surface will be sought through the techniques of electron spectroscopy for chemical analysis (ESCA) and far infrared analysis. In view of the importance of salivary glycoproteins in plaque-development, it is planned to continue our ongoing work on the adsorption of amino acid constituents of saliva on hydroxyapatite and to initiate research on the interaction of surface-active compounds which possess antimicrobial properties (e.g., chlorhexidine) with amino acid-coated hydroxyapatite. We plan to continue our current investigations on the measurement of thickness of thin protein films on fluorite and fluorapatite and also to determine the influence of adsorbed components of tobacco smoke on the dissoultion of hydroxyapatite in saliva and fluoride solutions.